1. Field of the Invention
The present invention relates to a clutch suitable for racing and, more particularly, to a uniquely designed long lever arm to be used in the clutch.
2. Description of the Prior Art
Racing clutches with long lever arms have one end portion of the lever which is internal of the yoke pivot point and the opposite end portion which is external. In these conventional designs, the lever arms are offset to the extent that the center of gravity is located substantially on the internal portion. In other words, a substantial part of the weight of the lever is located internally of the pivot point. The reason for this center of gravity offset is for ease of mechanical disengagement.
A problem existing for these devices is that as the clutch wears down (on the order of 0.015 inch) the position of the lever arm has to be adjusted to move the pressure plate further towards the clutch pack. For this amount of wear, it is usual to have a 11/2.degree. change in the lever angle. However, as the internal part of this lever arm moves up 11/2.degree., the external centrifugal force becomes less dominating and the internal centrifugal force becomes more dominating. This result occurs because each lever arm has a center of gravity point located on the internal position of the lever arm. As the centrifugal force increases, the center of gravity is pulled outwardly which in turn causes the lever arm to rotate about the pivot pin. This rotation of the lever arm causes the center of gravity to move farther out from the pivot point to form a larger moment arm which thereby increases the torque applied by the lever arm to the pressure plate.
Viewed along the axis of rotation of the rotating clutch assembly, the centers of gravity for each of the series of lever arms form a circle. As the rotation speed increases, the centrifugal force causes the circle to increase in diameter. This causes the opposite end of the lever arm to exert a greater force against the pressure plate, which in turn results in a greater plate load being exxerted than the driver desires for a given r.p.m. In other words, when the driver now reaches a given r.p.m. there will be more energy transmitted to the back wheels due to the new increased plate load, and this can cause the tires to spin. This transmission of a greater amount of energy is termed "violence" because there is now too much energy being transmitted at the same engine rate of speed as before. Again, this is because the lever arm has been moved up an additional angle of about 11/2.degree. from its initial offset of about 2.degree. to 3.degree. to compensate for the wear on the clutch and this has produced additional centrifugal torque.